7-11 crab gets its name from its array of spots

Published September 15, 2014 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2014 Susan Scott

This 7-11 crab was found in a Waia­lua tide pool. The crab is named for its spots — 11 total, with seven in front and on top, and four in back. ©2014 Susan Scott

I recently received an email with the subject “Crab on V-land beach.” (V-land, or Velzyland, is a North Shore surf spot.) Reader Bill Quinlan wrote, “I have attached two photos of a dead crab we found this afternoon. A lady we showed the crab to said she was from Kauai and they call that type of crab a 7-11 crab. She did not explain why.”

Oahu people call them 7-11 crabs, too. The striking species ranges throughout the Indian and Pacific Oceans on reefs from tide pools to 50 or so feet deep. Other names are spotted reef crab and dark finger coral crab. In Hawaii, though, and for many people around the world, it’s a 7-11 crab.

A common story about the unusual name is that it’s a reference to the crab’s maroon spots. Although some individuals have more, most crabs have seven spots across the shell’s front and top, and four across the lower back, totaling 11.

This logic would make it a 7-4 crab, but the words “seven-11” have more of a ring. A convenience store chain called Tot’m liked the rhyming words, as well.

In 1946 the name was changed to 7-Eleven to reflect its long (for the ’40s) operating hours, 7 a.m. to 11 p.m.

Two days after Bill’s email, I received another 7-11 crab email from my friend Mary. “This morning I found the remnants of a huge 7-11 crab on the reef at Ala Moana. His shell was about 8 inches across. First one I ever saw, living or dead. I understand from other locals there that about two years ago a lot of juveniles washed ashore. What an interesting world!”

It sure is. For unknown reasons, in July 2012 thousands of blueberry-size creatures washed ashore on Oahu. Being in their larval stage, the creatures didn’t look much like adult 7-11 crabs, but that was an expert’s conclusion. Check out the baby crabs at bit.ly/1CKYqFA.

I also found a 7-11 crab, but it was alive and well in a Waia­lua tide pool. After I took this picture, I put the little crab back in its pool to grow up and make more crabs. In Singapore the species is considered threatened due to pollution and over-collecting.

Seven-11 crabs grow to about 6 inches across, so the crab Mary found was as big as they get. She took it home to let the ants clean it outdoors before giving it a place of honor in the house.

Bill considered his crab a gem, too. “My wife, Rita, and I have been dive buddies for almost 40 years and have dived in numerous countries,” he wrote. “We both feel this is the most special crab we have ever seen. A graphic designer couldn’t come up with a design anywhere close to as good.”

I agree. A certain convenience store would do well to make this crab its logo.

Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2014 Susan Scott